WO 96/09589, assigned to the assignee of the present application, discloses a method and a device for extracting information from a database, according to which the data records of the database are examined, when a user has made a selection of a data element, in order to find all data element values which are implied by or consistent with the selection.
Table 1 in FIG. 1 shows an example of a database containing information about different clothes. It contains data elements of the types "Clothes", "Color", "Size" and "ArtNo". The data elements defined by the type "Clothes" may assume the value "shirt" and the value "jeans". Similarly, the data elements of the type "color" may assume the values "blue" and "red", the data elements of the type "size" the value "32", "35", "39" and "40", and the data elements of the type "ArtNo" the values "1001", "1003" or "2100". Before any selection at all has been made, all data elements are selectable. This is indicated in a number of status vectors (not shown), where all data elements ate marked as selectable by means of a predetermined status value.
Now assume that the user wants to know what clothes of size 39 are available. He then selects the data element value "39" of the type "size", e.g. by clicking on "39" in a list of all data element values of the type "size" displayed on a computer screen (not shown). In accordance with the method of WO 96/09589, the data element values "shirt", "blue", "1001", "red", "1103" will be found since they are implied by the selection. Thus, the user now knows that the available clothes of size 39 are a red shirt and a blue shirt having article numbers 1001 and 1003. The user also knows that there is no available pair of jeans of size 39, because the data element value "jeans" is excluded by the selection of the data element "39". When the database has been examined, the status values of those data elements that are excluded by the selection will be changed in the status vector to reflect the selection.
This example is of course a very simplified one, but the same principle may be used for more complex databases which include a large number of data elements.
In accordance with the method of WO 96/09589, the result of a selection may be presented by displaying, on the computer screen, the data element types and values which were found during the examination of the data records or by indicating, on the computer screen, the implied data element types and values by a color different from that used for the data element types and values not implied by the selection.
This presents no problem when the database contains a small number of data elements. When the database contains a large number of data elements of many different types, it may, however, be impossible to display all the data elements at the same time on the computer screen in a comprehensible way.
The above-mentioned problem occurs not only with the method of WO 96/09589, but in many cases where a large number of data elements are to be displayed on a computer screen area that is small compared with the number of data elements to be displayed and where each data element is defined by a data element type and a data element value and has an associated status value.